III.—Note on Fragments of Chert from North China

Extract

The fragments of partially weathered chert from North China sent by the Rev. S. Couling, unfortunately without indication of the particular locality or formation where they were collected, are of whitish, slate-grey, or pinkish aspect, and in two instances show traces of banded structure. They consist of cryptocrystalline or microcrystalline silica with small areas in which the silica is of a fibrous chalcedonic character. Remains of organisms can be distinguished in each of the four microscopic sections which have been prepared, but they are generally so shadowy and indefinite that their nature cannot be satisfactorily determined. Some portions of slide marked A are crowded with slender, straight, or slightly curved linear bodies, about .11 mm. in length by .01 mm. in width, which in places have a sub-parallel or sheaf-like arrangement. They might be supposed to be sponge spicules, but in their size and disposition they seem to differ from any fossil spicules with which I am acquainted. Slide C largely consists of numerous small, rounded, oval, and conical forms without walls, ranging from .1 to 1.7 mm. in diameter. In outline and in size many of these bodies might be compared to Radiolaria, but as they are now not sharply delimited from the clear matrix, but by a granular structure-without other features, it would be rash to assert, save upon further evidence, that they belong to these organisms. In slide D there are some well-defined circular bodies, .03 to .1 mm. in diameter, with clear solid walls, and not infrequently a central spot in each, which very much resemble transverse sections of sponge spicules, and it is possible that this may be their true nature, but some doubt rests on this owing to the apparent absence in the slide of longitudinal sections of spicules.